Corrugated fuel electrode

ABSTRACT

A fuel electrode incorporates a first and second corrugated portion that are attached to each other at offset angles respect to their corrugation axis and therefore reinforce each other. A first corrugated portion may extend orthogonally with respect to a second corrugated portion. The first and second corrugated portions may be formed from metal wire and may therefore have a very high volumetric void fraction and a high surface area to volume ratio (sa/vol). In addition, the strands of the wire may be selected to enable high conductivity to the current collectors while maximizing the sa/vol. In addition, the shape of the corrugation, including the period distance, amplitude and geometry may be selected with respect to the stiffness requirements and electrochemical cell application factors. The first and second corrugated portions may be calendared or crushed to reduce thickness of the fuel electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage entry of PCT/US2017/057552, filedOct. 20, 2017, which claims priority to U.S. Provisional Patent No.62/410,852, filed on Oct. 21, 2016. The subject matter of each of theseapplications is incorporated by reference herein in its entirety.

BACKGROUND Field

The invention relates to fuel electrodes for electrochemical powersystems and particularly to fuel electrodes for metal-air rechargeablepower systems.

Description of Related Art

Fuel electrodes for battery and power systems require contact with anionic conductive medium, such as an electrolyte and electrical couplingwith a current collector to allow current flow to and from the fuelelectrode. It is desirable in many systems to have a large surface areaof contact between the fuel electrode and the electrolyte to enableloading of fuel onto the electrode while minimizing thickness of thedeposited fuel. A fuel electrode with a very high surface-area-to-volumeratio (also called the surface to volume ratio and variously denotedsa/vol or SA:V, the amount of surface area per unit volume that amaterial occupies) is desirable. It is also desirable for this surfacearea to be readily accessible to the electrolyte and not small internalpores within the fuel electrode material, as this may presentlimitations to depositing of the fuel. In addition, it is desirable thatthe surface of the fuel electrode be smooth with limited corners as thismay be an area of charge concentration and can lead to dendriteformation. Fuel electrodes are usually made of metal and therefore ahigh specific surface area, surface area per unit mass, i.e. m²/g, isdesired to keep the cost of the fuel electrode down.

Porous metal fuel electrodes provide a high sa/vol but are costprohibitive in many applications and have irregularly shaped pores. Thepores within a porous metal span a wide range of sizes and present atortuous path from the exterior of the porous metal to the most interiorpores within the porous metal. This tortuous path to the internalsurface area, and smaller pores, can present flow restrictions of theelectrolyte and result in poor exchange and reaction rates. In addition,some of the pores within a porous metal fuel electrode can becomeblocked or clogged with deposits thereby reducing the effective sa/volratio over time as these clogged pores become unavailable for reaction.Electrolyte has to flow from the outside surface of the porous metalthrough a labyrinth of pores to reach pores and surface area within thedepth of the porous metal. Therefore, the structure of a porous metal,while having a high initial sa/vol ratio, may present mass transportlimitations, can have a reduced sa/vol ratio over time due to blockedpores, can have low electrolyte exchange or permeability of electrolytetherethrough, and can be cost prohibitive.

In addition, if the fuel electrode bows or flexes it can contact theopposite electrode and short out the system. Fuel electrodes made out ofsheets of material are susceptible to such deflection and bowing. Toprevent this, spacers or separators are often placed between the fuelelectrode and the opposing electrode, or cathode, to prevent shorting.The fuel electrode is sometimes in direct contact with a spacer whichreduces surface area available for reaction. Spacers add cost and canreduce the flow and mixing of electrolyte within the cell.

Furthermore, in some electrochemical systems, deposits, such asdendrites can form on the fuel electrode which can extend out from thesurface. If these dendrites contact the opposing electrode they canshort the system. The dendrites can also become dislodged from thesurface of the fuel electrode and fall to the bottom of the cell wherethey can also build up and extend over to the opposing electrode tocause a short.

Metal foams or 3D foams have been used, in some cases, to form part ofthe electrode structure. However, such foams are not ideal for a varietyof reasons, including, for example, producing irregularities, providingreduced open area, producing rough surfaces with sharp or undesirableangles and corners, and having lower surface area to volume ratios.

SUMMARY

One aspect of the present invention provides a fuel electrode for anelectrochemical cell. The electrode comprises a first corrugated portionformed of an electroconductive material. The first corrugated portionhas a first corrugation axis and comprises a plurality of aperturestherethrough. A second corrugated portion is formed of anelectroconductive material. The second corrugated portion has a secondcorrugation axis offset from the first corrugation axis and comprises aplurality of apertures therethrough. Electrode attachments attach thefirst and second corrugated portions to each other.

Another aspect of the invention provides an electrochemical cellcomprising the foregoing fuel electrode with metal fuel electrodepositedthereon, a cathode, such as an air electrode, and an ionicallyconductive medium between the fuel electrode and the cathode.

Other aspects, features, and advantages will become apparent from thefollowing detailed description, the accompanying drawings and theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention, andtogether with the description serve to explain the principles of theinvention.

FIG. 1 depicts a schematic view of an electrochemical cell having animmersed oxidant reduction electrode.

FIG. 2 depicts a schematic view of an electrochemical cell having anoxidant reduction electrode which defines a boundary wall for theelectrochemical cell.

FIG. 3 shows a surface image of metal foam.

FIG. 4 shows a cross sectional diagram of fuel deposition on a surfaceof metal foam.

FIG. 5 shows a cross-section of fuel deposition on a metal wire.

FIG. 6 shows a cross-section of fuel deposition of two smaller metalwires than shown in FIG. 5.

FIG. 7 shows a graph of the probability of dendrite formation versusthickness of fuel deposition.

FIG. 8 shows a graph of the thickness of fuel deposition versus amphours and two lines for different fuel electrodes.

FIG. 9 shows a metal screen that is flexible.

FIG. 10 show a corrugated metal screen that is flexible along one axisand stiffened by the corrugation in the opposing axis.

FIG. 11 shows a perspective view of an exemplary first corrugatedportion.

FIG. 12 shows a corrugation axis end view of the exemplary firstcorrugated portion shown in FIG. 11.

FIG. 13 shows a perspective view of an exemplary second corrugatedportion.

FIG. 14 shows a corrugation axis end view of the exemplary firstcorrugated portion shown in FIG. 13.

FIG. 15 show a perspective view of an exemplary fuel electrode having afirst corrugated portion attached to a second corrugated portion bydiscrete attachments.

FIG. 16 shows a corrugation axis end view of the exemplary fuelelectrode shown in FIG. 15.

FIG. 17 shows a perspective view of an exemplary first corrugatedportion having corrugation axis extensions that are larger incross-sectional dimension than the cross-corrugation extensions.

FIG. 18 shows cross-sectional views of the corrugation axis extensionand the cross-corrugation extension.

FIG. 19 shows a perspective view of an exemplary third corrugatedportion.

FIG. 20 shows a corrugation axis end view of the exemplary thirdcorrugated portion shown in FIG. 19.

FIG. 21 shows an end view of an exemplary corrugated fuel electrodehaving first, second and third corrugated portions attached to eachother and at offset angles.

FIG. 22 shows an end view of an exemplary corrugated fuel electrodehaving first, second and third corrugated portions attached to eachother and at offset angles and having different corrugation amplitudesand corrugation pitch.

FIG. 23 shows a perspective view of an exemplary first corrugatedportion having discrete apertures through the corrugated sheet material.

FIG. 24 shows an end view of an exemplary first corrugated portionhaving saw-tooth shaped corrugations or pleats.

FIG. 25 shows exemplary first, second and third corrugated portions atoffset corrugation axis angles.

FIGS. 26 and 27 show a side view of an exemplary fuel electrode havingfirst, second and third corrugated portions attached to each other andsloughed or dendritic material being captured in the corrugationsbetween adjacent corrugated portions.

FIGS. 28 and 29 show end views of an exemplary corrugated portion havinglinear segments at the peak and troughs of the corrugations.

FIG. 30 shows a first and second corrugated portion attached by a stitchline attachment that extends along the trough of the first corrugatedportion.

FIG. 31 shows a first and second corrugated portion attached by staplesalong the trough of the first corrugated portion.

FIG. 32 shows a first and second corrugated portion attached by weldattachments along the trough of the first corrugated portion.

FIG. 33 shows a schematic end view of an exemplary corrugated structureused as a fuel electrode and arranged with a cathode in anelectrochemical cell in accordance with an embodiment.

FIG. 34 shows a schematic end view of an exemplary corrugated structureused as a fuel electrode and arranged with a cathode in anelectrochemical cell in accordance with another embodiment.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Corresponding reference characters indicate corresponding partsthroughout the several views of the figures. The figures represent anillustration of some of the embodiments of the present invention and arenot to be construed as limiting the scope of the invention in anymanner. Further, the figures are not necessarily to scale and somefeatures may be exaggerated to show details of particular components.Therefore, specific structural and functional details disclosed hereinare not to be interpreted as limiting, but merely as a representativebasis for teaching one skilled in the art to variously employ thepresent invention.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Also, use of “a” or “an” are employed to describeelements and components described herein. This is done merely forconvenience and to give a general sense of the scope of the invention.This description should be read to include one or at least one and thesingular also includes the plural unless it is obvious that it is meantotherwise.

In cases where the present specification and a document incorporated byreference include conflicting and/or inconsistent disclosure, thepresent specification shall control.

Certain exemplary embodiments of the present invention are describedherein and are illustrated in the accompanying figures. The embodimentsdescribed are only for purposes of illustrating the present inventionand should not be interpreted as limiting the scope of the invention.Other embodiments of the invention, and certain modifications,combinations and improvements of the described embodiments, will occurto those skilled in the art and all such alternate embodiments,combinations, modifications and improvements are within the scope of thepresent invention.

Various portions of the electrochemical cell 100 may be of any suitablestructure or composition, including but not limited to being formed fromplastic, metal, resin, or combinations thereof. Accordingly, the cell100 may be assembled in any manner, including being formed from aplurality of elements, being integrally molded, or so on. In variousembodiments the cell 100 and/or the housing 110 may include elements orarrangements from one or more of U.S. Pat. Nos. 8,168,337, 8,309,259,8,491,763, 8,492,052, 8,659,268, 8,877,391, 8,895,197, 8,906,563,8,911,910, 9,269,996, 9,269,998 and U.S. Patent Application PublicationNos. 20100316935, 20110070506, 20110250512, 20120015264, 20120068667,20120202127, 20120321969, 20130095393, 20130115523, and 20130115525,each of which are incorporated herein in their entireties by reference.

FIG. 1 illustrates a schematic cross sectional view of anelectrochemical cell 100. As shown, the components of theelectrochemical cell 100 may be contained at least partially in anassociated housing 110. The cell 100 utilizes a liquid ionicallyconductive medium 124, such as an electrolyte 126, that is containedwithin the housing 110, and is configured to circulate therein toconduct ions within the cell 100. While at times the ionicallyconductive medium may be generally stationary within the housing 110,such as in a stagnant zone, it may be appreciated that the cell 100 maybe configured to create a convective flow of the ionically conductivemedium. In some embodiments, the flow of the ionically conductive mediummay be a convective flow generated by bubbles of evolved gas in the cell100, such as is described in U.S. Patent Publication No. 2013/0115532incorporated above in its entirety by reference

Although in the illustrated embodiment of FIG. 1 the cell housing isconfigured such that the oxidant reduction electrode 150 is immersedwith the oxidant reduction electrode module 160 into the cell chamber120, it may be appreciated that in various embodiments, otherconfigurations or arrangements of the cell 100 are also possible. Forexample, in FIG. 2, another embodiment of the cell 100 (specifically,cell 100*) is presented, whereby an oxidant reduction electrode 150*defines a boundary wall for the cell chamber 120, and is sealed to aportion of a housing 110* so as to prevent seepage of ionicallyconductive medium therebetween. In some such embodiments the convectiveflow of the ionically conductive medium in the cell chamber 120,described in greater detail below, may be in a direction upwards andaway from the oxidant reduction electrode 150*, across the top of thefuel electrode 130.

As shown in FIG. 3, a prior art metal foam 400 has metal fused togetherto form an interconnected network having pores 404. The pores arevariable in size. The structure has internal porosity or internalsurface area 402. Internal surface area is the surface area that extendsinto the outer surface or is beneath an outer surface. In addition,metal foam and sintered metal have irregularly shaped pores andsurfaces, many with rough or very low radius elements. The structure hasa large number of sharp edges or protrusions that can lead to theformation of dendrites.

FIG. 4 shows a dendrite 310 formed in the fuel deposition 300 layer onthe metal foam 400, as generally known in the art. The dendrite hasformed over the low radius of curvature element 409, or protrusion fromthe metal foam surface. As described herein, protrusion from the surfaceand or sharp corners may be areas of charge concentrations that can leadto dendrite formation. Also shown in FIG. 4 the internal surface area402 that may have limited or no fuel deposition. The fuel depositionlayer 300 on the surface of the metal foam may block the internalsurface area and prevent fuel deposition on the internal surfaces of themetal foam.

As noted previously, using these type metal foams or 3D foams as part ofthe electrode structure is not optimal or ideal because they result inirregularities, a reduced open area, rough surfaces with undesirableangles and/or corners, and a lower surface area to volume ratio.

As shown in FIG. 5, a fuel electrode comprises a fuel element, or metalwire 207, having diameter 209 and a fuel deposition layer 300 ofthickness 302 around the wire. In addition, a dendrite 310 has formed inthe fuel deposition layer.

As shown in FIG. 6, a fuel electrode comprises wires 207′ having asmaller diameter 209′ than the wire shown in FIG. 5. Again, there is afuel deposition layer 300 around the wires having a thickness 302′. Thethickness of the fuel deposition layer on each wire 207′ in FIG. 6 isless than the fuel deposition layer thickness in FIG. 5, but there ismore surface area for deposition in the fuel electrode of FIG. 6 becausemore wires of smaller diameter can be arranged in the same overallvolume. Therefore, the fuel is spread out over this larger surface areain a thinner layer.

FIG. 7 shows a graph of the probability of dendrite formation versusthickness of fuel deposition. As the thickness of fuel depositionincreases, the probability of dendrite formation increases. Therefore,for a given amount of deposition, the fuel electrode shown in FIG. 5 maybe above a threshold probability of dendrite formation whereas the fuelelectrode shown in FIG. 6 remains below the dendrite threshold limit.

FIG. 8 shows a graph of the thickness of fuel deposition versus amphours and two lines for different fuel electrodes. For a given number ofamp-hours, a fuel will be deposited over the available surface area ofthe fuel electrode and the fuel electrode in FIG. 6, having a highersurface area, will have a slower growth in the thickness of the fueldeposition layer. Therefore, the fuel electrode shown in FIG. 6 can runfor a longer time before exceeding the dendrite threshold limit andtherefore has a higher run capacity. However, the fuel electrode in FIG.6 comprises wires that are smaller in diameter, and therefore may bemore flexible or fragile, which is not desirable. The corrugatedelectrode, as described herein, can provide sufficient stiffness withsmaller diameter wire screens or other configurations.

A fuel electrode for an electrochemical cell comprises two or morecorrugated portions configured with their corrugation axes offset fromone another and attached to each other (also referred to as a“corrugated structure” throughout this disclosure) to produce a stiffercorrugated laminate fuel electrode preferably with high sa/vol. Rotatingthe corrugation direction of one corrugated portion relative to anotherenhances the structural rigidity of the fuel electrode. In addition, theopen area of the corrugated fuel electrode can be optimally tailored asdesired and may be uniform and provide little resistance to flowtherethrough. For example, the first corrugated portion may beconfigured vertically within the cell, wherein the first corrugationaxis extends from the top to the bottom of the cell and the secondcorrugated portion may be configured orthogonally to the firstcorrugated portion, wherein the second corrugation axis extendshorizontally, or across the cell. The axes need not align with thevertical/horizontal directions of the cell, and reference to thesedirections in the illustrated embodiment is for convenience. The firstand second corrugated portions may be attached to each other byattachments whereby the two attached corrugated portions support andreinforce each other to create a fuel electrode that is stiffer in thevertical and horizontal directions, or along the first corrugation axisand orthogonal to the first corrugation axis, as well as in torsion. Thesecond corrugated portion may be configured at a second corrugation axisoffset angle, i.e., its axis is offset at an angle relative to the firstcorrugation axis. In an embodiment, the second corrugation axis offsetangle is preferably at least about 30 degrees or more, about 45 degreesor more, about 60 degrees, 90 degrees or more or in any range betweenand including the offset angles provided. In an embodiment, the offsetof the second corrugation axis from the first corrugation axis isbetween about 25 degrees to about 90 degrees. In one embodiment, thesecond corrugation axis is about 45 degrees offset from the firstcorrugation axis. In another embodiment, the second corrugation axis isabout 90 degrees offset from the first corrugation axis. In anembodiment, the first corrugated portion and/or the second corrugatedportion may be calendared or crushed to reduce thickness of thecorrugated structure and/or the fuel electrode. A fuel electrode maycomprise any suitable number of corrugated portions including, but notlimited to, two or more, three or more, four or more, five or more, tenor more and any in range between and including the numbers provided.

A corrugated metal portion may comprise, consist essentially of, orconsist of an electrically conductive material including, metal, nickel,zinc, copper, aluminum, steel, platinum, gold, silver, palladium, platedmetal, nickel plated steel, nickel plated stainless steel and the like.A metal may be selected for a particular electrochemical applicationtaking into account the type of electrolyte, the conductivityrequirements as well as cost requirements.

FIG. 9 shows a fuel electrode 200 made of a metal screen 297 that isflexible. The metal screen is being rolled in the first axis 296 butcould also be rolled or easily flexed or bent in the perpendicularsecond axis 298. As used herein, the axis or axes in general refer tothe major or X-Y axes of the plane corresponding to the shape of theelectrode, and not the Z-direction of the thickness. A corrugation axismore specifically means the axis parallel to the direction in which thecorrugations extend.

As shown in FIG. 10, a metal screen 297 is corrugated to form a firstcorrugated portion 210 of a fuel electrode. The corrugations extend inthe corrugation axis 211, wherein the peaks and troughs of thecorrugations are aligned with this corrugation axis. The corrugatedportion is flexible and can be easily rolled or flexed in thecross-corrugation axis 212 as shown by the curved double arrow lineindicating the cross-corrugation axis. However, the first corrugatedportion will be stiffened and more resistant to flexing and bending inthe corrugation axis, as the corrugations increase the stiffness of themetal screen in that axis.

A woven screen or fabric couples the corrugation axis extensions andcross-corrugation extensions together through the weave itself. A meshmay comprise corrugation axis extensions and cross-corrugationextensions that are attached to each other by fasteners, adhesive,welding or soldering. The welded attachments may be discrete, such asspot welds. A weld attachment comprises fused materials, such as a firstand second corrugated portion being fused together. A metal wire from afirst corrugated portion may be welded to a metal wire of the secondcorrugated portion to form a weld attachment. Heat and pressure may beapplied to cause the compressed portions to fuse into each other.Diffusion welding may also be used. Diffusion welding is a solid statewelding process by which two metals, which may be dissimilar, can bebonded together. Diffusion involves the migration of atoms across thejoint, due to concentration gradients. Diffusion welding may bepreferred as it does not require as much heating as conventional weldingand therefore may produce a more robust attachment. Resistance weldingor ultrasonic bonding may also be employed to bond a first corrugatedportion to a second corrugated portion.

As shown in FIGS. 11 and 12, an exemplary first corrugated portion 210comprises corrugated-axis extensions 224 that extend in the firstcorrugation axis 211 and cross-corrugation extensions 226 that extend inthe first cross-corrugation axis 212, which is orthogonal to the firstcorrugation axis. In this embodiment, the corrugated-axis extensions andcross-corrugation extensions are strands, such as wire having a lengththat is much greater in dimension, such as at least 10 times greater,than a cross-sectional dimension of the strand. Apertures 222 are formedbetween the strands to allow flow of an ionic conductive medium, orelectrolyte therethrough. As shown in FIG. 12, the first corrugatedportion 210 has a first corrugation amplitude 218 or thickness 215between a first side 214 and a second side 216. The corrugation pitch221, or distance of a repeating unit of the corrugation is shown.

As shown in FIGS. 13 and 14, an exemplary second corrugated portion 230comprises corrugated-axis extensions 244 that extend in the secondcorrugation axis 231 and cross-corrugation extensions 246 that extend inthe second cross-corrugation axis 232. In this embodiment, thecorrugated-axis extensions and cross-corrugation extensions are strands,such as wire having a length that is much greater in dimension, such asat least 10 times greater, than a cross-sectional dimension of thestrand. Apertures 242 are formed between the strands to allow flow of anionic conductive medium, or electrolyte therethrough. As shown in FIG.14, the second corrugated portion 230 has a second corrugation amplitude238 or thickness 235 between a first side 234 and a second side 236. Thecorrugation pitch 241, or distance of a repeating unit of thecorrugation is shown.

As shown in FIGS. 15 and 16, an exemplary fuel electrode 200 has acorrugated structure including a first corrugated portion 210 attachedto a second corrugated portion 230 by attachments 280. The firstcorrugated portion has a first corrugation axis 211 that is about 90degrees offset from the second corrugation axis 231, wherein the firstand second corrugated portion are configured essentially orthogonally toeach other, with respect to their corrugation axes (although otherangles may be used). Apertures or open spaces through the first andsecond corrugated portions 222, 242 respectively, enable electrolyte toflow freely through the fuel electrode to allow high reaction rates. Asshown in FIG. 16, the fuel electrode 200 has a thickness 205 from afirst outer side 204 and a second outer side 206. The first corrugatedportion 210 is attached to the second corrugated portion 230 byattachments 280, such as discrete fasteners 282 that attach the twocorrugated portions together in one discrete location.

In an exemplary embodiment, the corrugated portions of the fuelelectrode made substantially of metal wire having a smooth continuousouter surface that is preferred for deposition of fuel thereon and theattachments of the fuel electrode may be made out of a materialdifferent than metal wire. A metal wire may be circular or oval incross-sectional shape having a radius of curvature about the outersurface, for example. The metal wire may optimally have essentially nointernal surface area, wherein the surface of the metal wire isessentially free of any porosity. The diameter of the strands, ormaximum cross-sectional dimension, may be about 0.5 mm or more, about 1mm or more, about 2 mm or more, about 3 mm or more about 5 mm or more,about 8 mm or more and any range between and including the diametersprovided. It is desirable to have a small diameter as this will increasethe surface area for fuel deposition, however the smaller the diameterthe more flexible the wire mesh or screen may be. Thus, a combination ofwire or strand diameters may be utilized in a corrugated portion or fromone corrugated portion to another, as described herein.

As shown in FIG. 17, an exemplary first corrugated portion 210 hascorrugation axis extensions 224 that are larger in cross-sectionaldimension than the cross-corrugation extensions 226. FIG. 18 shows thecross-sections of the corrugation axis extensions 224 and thecross-corrugation extensions 226. The corrugation axis extensions have agreater cross-sectional dimension 225 than the cross-corrugationextensions cross-sectional dimension 227. The corrugation axisextensions may be larger in diameter to reduce resistance for electricalcurrent collection, as these strands may be electrically coupled with acurrent collector 202 at the first end 228 or second end 229, as shown.

This ability to tailor the size and gap distance between corrugationaxis extensions and cross-corrugation extensions enables optionaltailoring of the corrugated portion to have optimized properties for theelectrochemical cell system. In addition, not all of the corrugationaxis extensions and cross-corrugation extensions have to be the same incross-section dimension. A portion of the corrugation axis extensionsmay be one diameter, and the remaining may be smaller in diameter, forexample.

In an embodiment, both of the first and second corrugated portions mayhave cross-corrugation extensions. An exemplary fuel electrode, inaccordance with an embodiment, has first and second corrugated portionsattached to each other, with the second corrugation axis being offsetfrom the first corrugation axis and the cross-corrugation extensions ofthe first and/or second corrugated portions may extend to a currentcollector (e.g., 202). In one embodiment, in this fuel electrode, thesecond corrugation axis may be between about 45 to about 90 degrees(both inclusive) offset from said first corrugation axis. In anembodiment, in the fuel electrode, the corrugation-axis extensions ofthe first corrugated portion are larger in cross-sectional dimensionthan the cross-corrugation extension of the first corrugated portion. Inan embodiment, the cross-corrugations extensions of the secondcorrugated portion are larger in cross-sectional dimension than thecorrugation-axis extensions of the second corrugated portion.

As shown in FIGS. 19 and 20, an exemplary third corrugated portion 250comprises corrugated-axis extensions 264 that extend in the thirdcorrugation axis 251 and cross-corrugation extensions 266 that extend inthe third cross-corrugation axis 252. In this embodiment, thecorrugated-axis extensions and cross-corrugation extensions are strands,such as wire having a length that is much greater in dimension, such asat least 10 times greater than a cross-sectional dimension of thestrand. Apertures 262 are formed between the strands to allow flow of anionic conductive medium, or electrolyte therethrough. As shown in FIG.20, the third corrugated portion 250 has a third corrugation amplitude258 or thickness 255 between a first side 254 and a second side 256. Thecorrugation pitch 261, or distance of a repeating unit of thecorrugation is shown. The third corrugated portion has a corrugationpeak 275 and corrugation trough 276, wherein the peak is the highestpoint and the trough is the lowest point of the corrugation, withrespect to a vertical axis 287 (also referred to as a thicknessdirection or Z-axis) and the corrugated portion extending perpendicularto said vertical axis 287.

As shown in FIG. 21, an exemplary fuel electrode 200 has a corrugatedstructure including first 210, second 230 and third 250 corrugatedportions attached to each other. The first and third corrugated portionsare aligned with the first and third corrugation axes aligned. Thesecond corrugation portion is configured between the first and thirdcorrugated portions and has a corrugation axis that is offset 90 degreesto the first and third corrugation axes. The first and third corrugationportions are attached to each other by attachments 280, both discretefasteners 283 and adhesive 281. The adhesive is attached to the twoadjacent corrugated portions and may extend around and encapsulate astrand of the corrugated portions.

As shown in FIG. 22, an exemplary fuel electrode 200 has a corrugatedstructure including first 210, second 230 and third 250 corrugatedportions attached to each other. Like FIG. 21, the first and thirdcorrugated portions 210, 250 are aligned with the first and thirdcorrugation axes aligned. The second corrugation portion 230 isconfigured between the first and third corrugated portions 210, 250 andhas a corrugation axis that is offset 90 degrees to the first and secondcorrugation axis. The first and third corrugation portions are attachedto opposite sides of the second portion 230 by discrete attachments 282.The amplitude and corrugation pitch of the three corrugated portions,however, are each different from one another. This may be done toprovide more surface area on one side versus the other, or to providemore stiffness in one direction than the other, for example. In anyembodiment with multiple corrugated portions, each adjacent pair ofcorrugated parties may have their corrugation axes angularly offset fromeach other, while the axes of alternating corrugated parties may beoffset or aligned.

In another embodiment, one of the second or third corrugated portions230, 250 may be configured at a 45 degree offset angle to the firstcorrugated portion 210 and the other corrugated portion is configuredwith a 90 degree offset angle to the first corrugated portion 210. Instill another embodiment, the fuel electrode may optimally comprise fourcorrugated portions with offset angles of 30 degrees, wherein when thefirst corrugated portion is configured vertically, one of the remainingcorrugated portions is configured with about a 30 degree offset angle,one is configured with about a 60 degree offset angle and the lastcorrugated portion is configured with about a 90 degree offset angle. Inthis embodiment, the fuel electrode may be stiffened in multipledirections to prevent deflection and bowing.

A corrugated portion may have a corrugation, or pleat that is saw-toothshaped having linear corrugation segments, whereby each corrugationforms a substantially triangular shape. A corrugation may be curved, orhave one or more radius portions. In an exemplary embodiment, acorrugation has a wave shape resembling a sinusoid or modifiedsinusoidal wave shape. A corrugation may consist of a sinusoidal waveshape that is modified to approach a trapezoidal wave shape. Acorrugation may have linear portions that extend along a peak and troughof the corrugation and connection segments that extend substantiallyvertically (i.e. in the Z-direction or thickness of the individualportion) between the peak and trough segments or at some offset anglewith respect to vertical. A ratio of the amplitude to the pitch is thecorrugation ratio, which defines how packed or spaced out thecorrugations are. For example, a corrugation ratio of one means that theamplitude and pitch are equal, whereas a corrugation ratio of two meansthat the corrugation is twice as tall as it is wide. A highercorrugation ratio will create a higher sa/vol of the corrugated portion,whereby more material is within the volume defined by the product of theamplitude, the width and the length of the corrugated portion. A lowcorrugation ratio may be less desirable as it will not be as stiff.Stiffness of a corrugated portion in a direction orthogonal to thecorrugation axis is increased by a higher corrugation ratio.

The corrugation ratio may also influence the ability of a corrugatedportion to capture formations, dendritic material for example, that mayslough or fall off the surface of a corrugated portion. A corrugatedportion may have a corrugation ratio of about 0.25 or more, about 0.5 ormore, about 0.75 or more, about 1.0 or more, about 1.5 or more, about2.0 or more, about 3.0 or more, about 5 or more, about 10 or more andany ratio between and including the exemplary ratios provided. Inaccordance with an embodiment, a corrugated portion may have acorrugation ratio between about 0.25 and about 10.0 (both inclusive). Inone embodiment, a corrugated portion may have a corrugation ratiobetween about 0.25 and about 5.0 (both inclusive). In one embodiment, acorrugated portion may have a corrugation ratio between about 0.25 andabout 5.0 (both inclusive). In another embodiment, a corrugated portionmay have a corrugation ratio of no more than about 3.0 (inclusive). Theactual amplitude and pitch dimension may be selected based on the sizeof the electrochemical cell but in many cases will be on the order ofabout 0.1 cm or more, about 0.25 cm or more 0.5 cm or more, about 1 cmor more, about 2 cm or more, about 3 cm or more, about 5 cm or more andany range between and including the values provided. In an embodiment,the amplitude may be between about 0.1 cm and about 3.0 cm (bothinclusive). In one embodiment, the amplitude may be between about 0.1 cmand about 1.5 cm (both inclusive). In an embodiment, the pitch may bebetween about may be between about 0.1 cm and about 3.0 cm (bothinclusive). In one embodiment, the amplitude may be between about 0.1 cmand about 1.5 cm (both inclusive).

As shown in FIGS. 23 and 24, an exemplary first corrugated portion 210comprises a corrugated sheet of material 223 having apertures 222through the sheet of material. The sheet of material may be a sheet ofmetal. The corrugations are saw-tooth shaped having linear segments 271,272 that create triangular shaped corrugations 270 or pleat segments.The corrugations extend in the first corrugation axis 211 and thecross-corrugation axis 212 is orthogonal or perpendicular to the firstcorrugation axis. In a non-limiting embodiment, apertures 222 are formedthrough the corrugated sheet along a first corrugation segment 271 andnot along the second corrugation segment 272, and allow flow of an ionicconductive medium, or electrolyte therethrough. The location, number orareal density, and shape of the apertures may be selected to providesuitable flow of electrolyte therethrough. In addition, the location ofthe apertures may be selected to produce a flow direction of electrolytethrough the fuel electrode, wherein the flow may be up to preventdislodging of slough or dendritic material. As shown in FIG. 24, thefirst corrugated portion 210 has saw-toothed shaped corrugations orpleats, having linear corrugation segments. The saw-toothed shapedcorrugations have corrugation peaks 275 and corrugation troughs 276. Thefirst corrugated portion 210 has a first corrugation amplitude 218 orthickness 215 between a first side 214 and a second side 216. Thecorrugation pitch 221, or distance of a repeating unit of thecorrugation, as well as the sheet thickness 217 are shown.

The apertures 222 may be formed by punching, cutting, laser cutting,water cutting and the like. In an exemplary embodiment, a sheet is anexpanded sheet of metal, wherein the metal sheet is perforated or cutand then stretched to form opening in the sheet material, usuallydiamond shaped openings. Expanded metal is an inexpensive method offorming a permeable metal sheet of material that can then be corrugatedor pleated to form a corrugated portion.

FIG. 25 shows exemplary first 210, second 230 and third corrugatedportions 250 each at offset corrugation axis angles relative to oneanother. The second corrugated portion 230 is at a second corrugationaxis offset angle 233 from the first corrugated portion. The thirdcorrugated portion 250 is at a first-to-third corrugation axis offsetangle 253 from the first corrugated portion and at a second-to-thirdcorrugation axis offset angle 273 from the second corrugated portion. Inthis embodiment, the second corrugated portion is at an offset angle ofabout 45 degrees from the both the first and third corrugated portionsmaking the third corrugated portion orthogonal to the first corrugatedportion. As described herein the offset angles may be selected forrigidity, flow, and/or electrical conductively purposes.

As shown in FIGS. 26 and 27, an exemplary fuel electrode has acorrugated structure having first 210, second 230 and third corrugatedportions 250 attached to each other with sloughed 290 or dendriticmaterial 292 being captured in the corrugations between adjacentcorrugated portions. The fuel electrode has a corrugated electrodeportions having strands in the middle as the second corrugated portion230, and FIG. 26 shows corrugated portions formed out of a sheet ofmaterial having apertures on the outside as the first and thirdcorrugated portions 210, 250. The apertures in the first 210 and third250 corrugated portions, or the outer corrugated portions, may beconfigured in the second corrugation segment 272 to produce an upwardflow through the fuel electrode, as indicated by the large arrows.Alternatively, the apertures may be formed only in the first corrugationsegments 271, the upper segments, of the outer corrugated portions 210,250 to prevent any sloughed 290 or dendritic material 292 from fallingdown and out through the apertures. With apertures only on the upperportion of the pleat segment, slough material may not be able to falldown through the corrugated portions to the bottom 203 of the fuelelectrode. That option is beneficial because it keeps the slough metalin contact with the electrode for oxidation. The first end 228 andsecond end 229 of the fuel electrode 200 is electrically coupled with acurrent collector 202, 202′ at the top 201 and bottom 203 of the fuelelectrode, respectively.

As shown in FIGS. 28 and 29, exemplary corrugated portion 210 has linearsegments at the peak 275 and troughs 276 of the corrugations 270. Alinear peak segment 277 and linear trough segment 278 extend essentiallyin the cross-corrugation axis direction and are coupled together bypeak-trough connectors 279 that are at an offset angle 288 to thevertical axis as shown in FIG. 28, and that are substantially verticalas shown in FIG. 29. These types of corrugations may provide a highlevel of rigidity about the cross-corrugation axis.

FIG. 30 shows a first corrugated portion 210 and second corrugatedportion 230 attached by a stitch line attachment 286 that extends alongthe corrugation trough 276 of the first corrugated portion. The stitchline attachment is an example of a continuous attachment 284 (as opposedto discrete attachments at spaced apart points. The stitch line extendsalong the corrugation axis 211 of the first corrugated portion 210. Thestitches may extend down and pull the peaks 275′ of the secondcorrugated portion 230 to the troughs 276 of the first corrugate portionto firmly attach the two corrugated portions together.

The continuous stitched seam may optimally comprise at least 10 stitchesmade by the continuous thread that joins a first and second corrugatedportion together. A thread may be a synthetic material, such as apolymeric material that is substantially non-reactive in theelectrolyte, such as a fluoropolymer, polypropylene and the like. Athread may be a conductive material, such as a metal wire that bothphysically and electrically couples a first and second corrugatedportion together. A thread may be stitched in a discrete or continuousmanner to connect a first and a second corrugated portion together. Athread may be a supple material that is not free standing, whereby thethread will not hold a shape when a small compressive or flexural loadis applied, such a gravity. For example, a thread may flex and deformwhen not supported by a surface.

FIG. 31 shows a first corrugated portion 210 and second corrugatedportion 230 attached by staples 294 as discrete attachments along thecorrugation trough 276 of the first corrugated portion. The staples mayextend from a trough of the first corrugated portion and into the peaks,or proximal to the peaks of the second corrugated portion, wherein thepeak of the second corrugate portion is adjacent the trough of the firstcorrugated portion. Any number or staples may be used to attach thefirst corrugation portion to the second corrugated portion and thestaples may electrically couple the first and second corrugated portionstogether.

A staple may be metal or an electrically conductive material thatphysically and optionally electrically couples the first and secondcorrugated portions together. Staples may be attached along a trough ofa first corrugated portion to the second corrugated portion, forexample. A staple may be free standing, wherein the staple maintains ashape under small loads, such as gravity.

FIG. 32 shows a first corrugated portion 210 and second corrugatedportion 230 attached by discrete weld attachments 295 configured alongthe corrugation trough 276 of the first corrugated portion. The weldattachments may be spot welds that attach the first and secondcorrugated portions together in discrete locations, or spots. A wire 298of the first corrugated portion 210 may be welded with a wire 299 of thesecond corrugated portion 230. Any number or weld attachments 295 may beused to attach the first corrugation portion to the second corrugatedportion and the weld attachments may electrically couple the first andsecond corrugated portions together.

An electrically conductive attachment, such as welding a thread in astitch or stich line, or a staple, may provide electrical connectionsbetween the two corrugated portions and therefore reduce electricalresistance which may promote uniform fuel deposition.

Any of the embodiments disclosed herein may include corrugated portionsthat are calendared or crushed. In an embodiment, two or more corrugatedportions may be calendared or crushed together to reduce thickness ofthe corrugated structure and thus the fuel electrode For example, afterpositioning the corrugated portions at an angle relative to one another,pressure may be applied to the structure (e.g., via a mechanical pressor other pressure application device) to crush, e.g., corrugation-axisextensions and/or cross corrugation extensions of, the corrugatedportions. In one embodiment, at least a portion of some of theextensions in the corrugated portions are non-linear and/or changed ortransformed from their original structural configuration aftercalendaring or crushing. In an embodiment, the thickness of thecorrugated structure is reduced approximately 5% to approximately 50%from its original thickness (i.e., a thickness before pressure isapplied to the corrugated portions). In one embodiment, the thickness ofthe corrugated structure is reduced approximately 10% to approximately20% from its original thickness (i.e., a thickness before pressure isapplied to the corrugated portions).

Crushing or calendaring the corrugated portions provides a numberbenefits, including decreasing a thickness of the corrugatedstructure/fuel electrode, increasing a surface area per unit thickness,and a higher surface area to volume ratio. Crushed or calendaredcorrugated portions can also allow improved performance. For a givenelectrode surface area and a given inter-electrode gap (e.g. thedistance between the air cathode and the near side of the anode/fuelelectrode) reducing thickness can allow for shifting of the center ofmass of the fuel electrode closer to the other electrode (i.e. the OEE(oxygen evolving electrode) or other charging electrode during charge orair cathode during discharge), while maintaining the same total fuelloading/capacity. This reduces total IR drop through the electrolyte,thereby reducing cell voltage during charge and increasing cell voltageduring discharge. Alternatively, increasing surface area, for a giventhickness and inter-electrode gap will decrease overpotential due tolower current density, leading to improved cell voltage. Cycling mayalso be improved while using a crushed/calendared corrugated structure.For example, if the center of mass of the fuel electrode is unchanged,the reduced thickness implies increased inter-electrode gap, which mayaid in cyclability and reducing the tendency and probability ofshorting, without adversely affecting performance (i.e. cell voltage).Increasing area/unit thickness can also lead to more uniform plating(charge) and oxidation (discharge) of the fuel electrode, since thedifference in the electrode gap (i.e. as measured between the front andback sides of the fuel electrode) is reduced.

Also, if the total surface area of the corrugated structure is increasedand crushed to the same thickness as the lower surface area, uncrushedanode/fuel electrode, the loading of the fuel on the anode (i.e. totalmass or cell capacity) can be increased and improved. This results inincreased energy density when concentration of the fuel species in theelectrolyte is also increased. Further, increasing the electrode areawhile maintaining the same loading may result in reduced charge anddischarge current densities. This tends to increase both performance andcyclability, while still maintaining large enough inter-electrode gapscritical for good cycling. The higher surface area for a given capacityalso reduces average film thickness, film thickness non-uniformity andassociated film stresses, which is important for achieving good cycling.

In addition to a corrugated structure being able to reduce shortage, acrushed/calendared corrugated structure may further reduce a cell'ssusceptibility to shortage by reducing an amount and size of dendritesthat may be dislodged from the surface of the fuel electrode, and intothe ionically conductive medium and housing.

Moreover, as generally noted throughout this disclosure, the hereindescribed corrugated structure(s) (i.e., two or more corrugationportions assembled at an offset angle relative to one other, e.g., firstand second corrugated portions) not only provide rigid structures withhigh surface area to volume ratios that may be used as fuel electrodes,but also allow for tailoring of the fuel electrode design. For example,the diameters (of wires or elements), weave density (e.g., wires perinch), the corrugation amplitude and/or pitch, the orientation and/ornumber of corrugated screens/portions bonded/attached together may bealtered to change and tailor any number of features, including: surfacearea to volume ratio, structure conductivity, open area fraction, thecorrugated structure stiffness or strength (resistance to bending), openvoid fraction, structure thickness, and total project structure surfacearea. Using smooth portions or wires also leads to smoother fueldeposition and better cell cycling.

Any of the herein described embodiments of a corrugated structure may beused as a fuel electrode/anode in an electrochemical cell having acathode and an ionically conductive medium communicating the fuelelectrode. FIG. 33 shows an example arrangement of a corrugatedstructure (e.g. as shown in FIG. 16) provided as the fuelelectrode/anode relative to a cathode (e.g., air electrode) and anyother electrodes (e.g., OEE) (all of which are provided in a cellhousing along with an ionically conductive medium) in an electrochemicalcell, in accordance with an embodiment. The current collector (e.g. 202)or busbar is attached to the proximal corrugated portion (or screen),i.e., the portion of the corrugated structure that is closest to thecathode.

Furthermore, since each of the embodiments of the disclosed corrugatedstructure is a composite structure, assembled from individual corrugatedscreens that are coupled together via spot welds, staples, stitches,etc., electrical conductance through and across the corrugated structurecan be varied by: (i) coupling individual screens that have differentelectrical resistance (i.e., different pitch and/or diameter), (ii) howthe structure is bussed ((e.g. bussing all screens together, bussingonly the screen proximal to the OEE or cathode, bussing only the screendistal from OEE or cathode), and/or (iii) changing the type and/ordensity of the attachment points between individual screens, forexample. This may further allow control over the distribution of fuelover the anode/fuel electrode, which may be advantageous for improvedcyclability. For example, as shown in FIG. 34, a corrugated structuremay be provided or assembled as a fuel electrode/anode in an invertedconfiguration as compared to the one shown in FIG. 33; i.e., thecorrugated structure may be arranged with a cathode and any otherelectrodes (e.g., OEE) in a cell such that the current collector (e.g.,202) or busbar is attached only to the distal corrugated portion (orscreen), i.e., the portion of the corrugated structure that is farthestaway from the cathode, or, in other words, the corrugated portion thatis on an opposite or outer side of the structure relative to the side atwhich the cathode is nearest. Assembling the anode/fuel cell in thismanner may improve cycling within the cell.

When used herein, the terms “peak and “trough” are used for conveniencein reference to the Figures are not intended to imply that there isnecessarily any structural difference between the two or any particularorientation, and thus there is no requirement of a “peak” verticallyhigher than any “trough”. Hence, these terms should be interpreted todenote a specific orientation for the fuel electrode. They could also bereferred to as peaks on the first and second side because a trough isessentially a peak on the opposite sides. Whatever terminology is usedis simply for convenience in reference to the Figures. In manyembodiments the fuel electrode will be in a vertical orientation.

It will be apparent to those skilled in the art that variousmodifications, combinations and variations can be made in the presentinvention without departing from the spirit or scope of the invention.Specific embodiments, features and elements described herein may bemodified, and/or combined in any suitable manner. Thus, it is intendedthat the present invention cover the modifications, combinations andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

The open area percentage of a corrugated portion, the percent of thearea that is open or represented by apertures, may optimally beengineered with respect to the amount of flow that will be requiredthrough the corrugated portion as well as the other factors of thecorrugated portion including the corrugation ratio, amplitude and pitchdimensions. An exemplary corrugated portion or corrugated fuel electrodemay have an open area percentage of about 50% or more, 75% or more,about 85% or more, about 90% or more, about 95% or more and any rangebetween and including the open area percentages provided. In accordancewith an embodiment, the corrugated portion(s) and/or corrugated fuelelectrode may have an open area percentage between about 50% to about95% (both inclusive). A corrugated electrode may have open area thatextends completely through the electrode, from a first side to a secondside, whereby a straight line can be drawn from a first side to secondside through said open area. A corrugated portion or the fuel electrodemay be effectively permeable to allow electrolyte to flow therethrough.In an embodiment, each of the corrugated portions used to form the fuelelectrode may have a larger open area percentage while, after theirassembly (and offset), the fuel electrode has a smaller open areapercentage than the individual corrugated portions. For example, in oneembodiment, each of the corrugated portions may have an open areapercentage of about 50% to 95%; the fuel electrode formed using saidcorrugation portions may have an open area percentage of about 5% toabout 80%, in accordance with an embodiment. In one embodiment, thecorrugation portion and/or fuel electrode may have a permeabilitythrough the plane of the material that is between about 100 Frazier andabout 500 Frazier, including the Frazier values provided.

A fuel electrode made from two or more corrugated portions that areattached to each other may have a volumetric void fraction, thepercentage of the volume defined by the fuel electrode that is openspace, that is high to enable good transport and flow of electrolytetherethrough. The volume of the fuel electrode is defined by the productof the outside dimension thickness, length and width of the fuelelectrode. An exemplary corrugated portion may have a volumetric voidfraction of about 75% or more, about, about 85% or more, about 90% ormore, about 95% or more and any range between and including thepercentages provided. In an embodiment, the fuel electrode has avolumetric void fraction between about 80% and 99.5% (both inclusive).In another embodiment, the fuel electrode has a volumetric void fractionbetween about 90% and about 99.5% (both inclusive). In yet anotherembodiment, the fuel electrode has a volumetric void fraction betweenabout 95% and about 99.5% (both inclusive).

It is desirable to maximize reaction surface area per volume, sa/vol, ofthe corrugated portions and/or fuel electrode and enable effectiveexchange of the ionic fluid or electrolyte. An exemplary corrugatedportion or corrugated fuel electrode may optimally have a surface areato volume ratio, sa/vol, of about 0.5 of more, about 1 or more, about 5or more, about 10 or more and any range between and including the sa/volvalues provided. In an embodiment, the corrugation portion(s) and/or thefuel electrode has a sa/vol between about 0.25 and about 30 (bothinclusive). In another embodiment, the corrugation portion(s) and/or thefuel electrode has a sa/vol between about 1.0 and about 10 (bothinclusive). In yet another embodiment, the corrugation portion(s) and/orthe fuel electrode has a sa/vol between about 2.0 and about 6.0 (bothinclusive). In one embodiment, the corrugation portion(s) and/or thefuel electrode has a sa/vol of about 1.0. In one embodiment, thecorrugation portion(s) and/or the fuel electrode has a sa/vol of about3.0. This value (sa/vol) can be calculated approximately by taking intoaccount the diameter of the wire and the number of wires per unit lengthin both length and width direction as well as the volume occupied by thecorrugated electrode, such as the amplitude of the corrugated portionsthat are attached multiplied by the area, length and width, occupied bythe electrode. For example, a woven screen with a size of 24 by 27 by0.6 cm utilizing round cross-sectional wires has a surface area of about1,400 cm2 and a volume of about 389 cm3. This example has a sa/vol ofabout 3.6 cm2/cm3. The density of an exemplary corrugated electrodehaving first and second corrugated portions made out of woven screenhaving circular cross section wires with a diameter of about 3 mm andsubstantially square openings having a distance of 5 mm is about 0.065g/cc, or 0.8% the density of solid nickel.

It will thus be seen that the features of this disclosure have beenfully and effectively accomplished. It will be realized, however, thatthe foregoing preferred specific embodiments have been shown anddescribed for the purpose of illustrating the functional and structuralprinciples of this disclosure and are subject to change withoutdeparture from such principles. Therefore, this disclosure includes allmodifications encompassed within the spirit and scope of the followingclaims.

What is claimed is:
 1. A rechargeable electrochemical cell comprising: ametal fuel electrode comprising: a) a first corrugated portion formed ofelectrically conductive material, the first corrugated portion having afirst corrugation axis and comprising a plurality of aperturestherethrough; b) a second corrugated portion formed of electricallyconductive material, the second corrugated portion having a secondcorrugation axis that is offset from said first corrugation axis andcomprising a plurality of apertures extending therethrough; and c)electrode attachments attaching the first corrugated portion and thesecond corrugated portion to each other; an air cathode for reducingoxygen during discharging; an ionically conductive medium communicatingthe metal fuel electrode and the cathode; and an oxidable metal fuel forelectrodeposition on the corrugated portions of the metal fuel electrodeduring charging and for oxidation at the metal fuel electrode duringdischarging, wherein the metal fuel electrode with the oxidable metalfuel thereon and the air cathode constitute a metal-air cell.
 2. Therechargeable electrochemical cell of claim 1, wherein the offset of thesecond corrugation axis from the first corrugation axis is between about25 degrees to about 90 degrees.
 3. The rechargeable electrochemical cellof claim 1, wherein the second corrugation axis is about 45 degreesoffset from said first corrugation axis.
 4. The rechargeableelectrochemical cell of claim 1, wherein the second corrugation axis isabout 90 degrees offset from said first corrugation axis.
 5. Therechargeable electrochemical cell of claim 1, wherein the corrugatedportions comprise a surface area to volume ratio (sa/vol) between about0.5 and about 10.0.
 6. The rechargeable electrochemical cell of claim 1,wherein the corrugated portions comprise a surface area to volume ratio(sa/vol) between about 0.25 and about 30.0.
 7. The rechargeableelectrochemical cell of claim 6, wherein the corrugated portionscomprise a surface area to volume ratio (sa/vol) of about 1.0 and about10.0.
 8. The rechargeable electrochemical cell of claim 1, whereincorrugated portions comprise an open surface area between about 50% toabout 95%.
 9. The rechargeable electrochemical cell of claim 1, whereinthe metal fuel electrode has a volumetric void fraction between about90% to about 99.5%.
 10. The rechargeable electrochemical cell of claim1, wherein at least one of the first corrugated portion and the secondcorrugated portions comprises a sheet having the apertures therethrough,wherein said sheet has a substantially uniform thickness.
 11. Therechargeable electrochemical cell of claim 1, wherein at least one ofthe first corrugated portion and the second corrugated portion comprisesa screen.
 12. The rechargeable electrochemical cell of claim 11, whereinthe screen is a woven screen.
 13. The rechargeable electrochemical cellof claim 11, wherein the first corrugated portion and second corrugatedportion comprise corrugation-axis extensions and cross-corrugationextensions.
 14. The rechargeable electrochemical cell of claim 13,wherein the corrugation-axis extensions and cross-corrugation extensionsare wires.
 15. The rechargeable electrochemical cell of claim 13,wherein both the first and second corrugated portions are screens andthe corrugation-axis extensions of the first corrugated portion extendand connect to a current collector.
 16. The rechargeable electrochemicalcell of claim 1, wherein the first corrugated portion has a firstcorrugation ratio and the second corrugated portion has a secondcorrugation ratio, wherein both the first and second corrugation ratiosare greater than 0.75 and no more than about 5.0.
 17. The rechargeableelectrochemical cell of claim 1, wherein the electrode attachments arestitches.
 18. The rechargeable electrochemical cell of claim 1, whereinthe electrode attachments comprise a staple that extends from the firstcorrugated portion around a portion of the second corrugated portion.19. The rechargeable electrochemical cell of claim 1, wherein theelectrode attachments comprise a weld attachment that comprises thefirst corrugated portion fused to the second corrugated portion.
 20. Therechargeable electrochemical cell of claim 1, further comprising: a) athird corrugated portion formed of an electrically conductive material,the third corrugated portion having a third corrugation axis that isoffset from said second corrugation axis and having a plurality ofapertures extending therethrough; wherein the third corrugated portionand said first and second corrugated portions are attached to each otherby said electrode attachments.
 21. The rechargeable electrochemical cellof claim 1, wherein the first corrugated portion and second corrugatedportion are each a metal screen.
 22. The rechargeable electrochemicalcell of claim 14, wherein the wire has essentially no internal surfacearea.
 23. The rechargeable electrochemical cell according to claim 1,wherein the first corrugated portion and the second corrugated portionare calendared or crushed together.
 24. The rechargeable electrochemicalcell according to claim 1, further comprising a charging electrode. 25.The rechargeable electrochemical cell according to claim 1, wherein thefirst corrugated portion and the second corrugated portion arecalendared or crushed together.
 26. A fuel electrode for a rechargeableelectrochemical cell, comprising: a) a first corrugated portion formedof electrically conductive metal material, the first corrugated portionhaving a first corrugation axis and comprising a plurality of aperturestherethrough; b) a second corrugated portion formed of electricallyconductive metal material, the second corrugated portion having a secondcorrugation axis that is offset from said first corrugation axis andcomprising a plurality of apertures extending therethrough; and c)electrode attachments attaching the first corrugated portion and thesecond corrugated portion to each other; wherein an oxidable metal fuelis electrodeposited on the fuel electrode for oxidation at the fuelelectrode during discharging, wherein the electrically conductive metalmaterial of each corrugated portion has a smooth continuous outersurface with essentially no internal surface area and receives theelectrodeposited metal fuel thereon during charging.
 27. The fuelelectrode of claim 26, wherein at least one of the first corrugatedportion and the second corrugated portion is a screen.
 28. The fuelelectrode of claim 27, wherein the screen is a woven screen.
 29. Thefuel electrode of claim 27, wherein the screen is formed ofcorrugation-axis extensions and cross-corrugation extensions.
 30. Thefuel electrode of claim 29, wherein the corrugation-axis extensions andcross-corrugation extensions are wires of the electrically conductivemetal material having essentially no internal surface area.
 31. Arechargeable electrochemical cell comprising: the fuel electrodeaccording to claim 26; an air cathode for reducing oxygen duringdischarging; an ionically conductive medium communicating the fuelelectrode and the cathode; and an oxidable metal fuel forelectrodeposition on the corrugated portions of the fuel electrodeduring charging and oxidation at the fuel electrode during discharging,wherein the fuel electrode with the oxidable metal fuel thereon and theair cathode constitute a metal-air cell.
 32. The rechargeableelectrochemical cell according to claim 31, further comprising acharging electrode.
 33. The rechargeable electrochemical cell accordingto claim 1, wherein the oxidable metal fuel is configured to beelectrodeposited on the corrugated portions of the fuel electrode.